Our experience of time is helpful as an illustration here. Russell describes the "feeling of duration" as a "notoriously unsafe" guide to actual time "by the clock." When we are in pain or bored, time passes very slowly, and it flies when we are happy or busy. A public time and a private time seem distinct, just as public and private space. Our perception of the "time-order," in which events occur, seems to correspond to an actual order.

When there exists a relation of correspondence between "sense-data with their physical counterparts," we can reasonably assume that our perception of a quality like redness depends, somehow, on the physical object. However, beyond this, we have no knowledge of the physical object. Russell states that "although relations of physical objects have all sorts of knowable properties, derived from their correspondence with the relations with sense- data, the physical objects themselves remain unknown in their intrinsic nature, so far at least as can be discovered by means of the senses."


Russell admits that the most natural hypothesis to endorse is that physical objects, while not exactly identical, seem more or less similar to our sense- data. This view offers a direct, substantial equivalency of the form: 'we see what is'. Our natural inclination is "not ultimately the most defensible," and Russell concludes with a gesture toward other philosophical attempts to construe the nature of matter. The idealists, who held that "what appears as matter is really something mental," become his new target.

In this section Russell clearly articulates his division between a scientific world of matter and a world of experience, just one instance of his dichotomy of the world. One feature of Russell's theory of perception expressed here is the idea that we grasp reality when we are in a "suitable relation" to the physical world. We understand it indirectly, in a way distinct and opposable to the current philosophical trend, which advocates direct realism.